1. Field of the Invention
My invention relates to the field of signals processing, and more specifically to integrating optical processors capable of performing correlations and similar computational functions.
2. Description of the Prior Art
Large bandwidth communications signals are routinely used to convey vast quantities of information. An important step of the information extracting process in many cases is to correlate the received signal with some other signal. For example, the auto-correlation of a received radar signal with the original transmitted signal will yield data related to the distance to some object. The cross-correlation of an unknown signal with a known standard will yield useful data on the unknown signal and its information. The effective utilization of correlation techniques for signals analysis requires rapid, and sometimes even real-time, processing. The necessary processing speeds, while often beyond the capabilities of digital computers, may be obtained by optical processors.
A common and highly effective device for imparting information in an electrical signal onto an optical beam is an acousto-optical modulator, commonly known as a Bragg cell. U.S. Pat. No. 4,225,938 to Turpin discloses a time-integrating optical processor utilizing two one-dimensional Bragg cells. An undesirable attribute of that structure is an undesirable constant level of bias in the output image. Pending patent application Ser. No. 257,061, filed Apr. 24, 1981 by Cohen, discloses a space-integrating optical processor. Applications exist which require a finer degree of frequency resolution than has been found to be possible with that structure. It is desirable to have an optical signals processor capable of overcoming the above deficiences of the prior art.